Vintage Dirt Bike Q & A

1976 model with about 4,000 miles....rarely driven maybe 50 miles a year.....take out of storage last week, charge battery, fires right up and runs good as always......tonight after riding around town head out riding on the highway doing 60mph for about 10 minutes then all of sudden lose power and bike cuts off.....will not crank....plenty of gas,good battery...

what do you guys think?

We need more information. Did it lock up?? Did you pull the plug and inspect it?? What does it look like?? Were you using fresh gas?? Air filter clean??
In the end, it's either spark (or plug); fuel (or carb); air (filter, but I seriously doubt it); or mechanical. Start with quick mechanical: does it kick over smoothly; Then check the plug. Try a new one. See if it sparks when you kick it over; then make sure fuel flows smoothly from the tank petcock; then inspect and clean the carb. And of course, inspect and clean the air filter if it needs it. Once you narrow it down, the guys here can give more assistance.
Oh, are you using pre-mix or injection for the oil?? If injection, make sure you have oil and it is working properly. If pre-mix, what are you mixing it at?

Did not lock up,kicks over but not spark
gas is from last fall but rode 5 miles no probs
using the stock oil injector and has oil
out of town right now but will pull plug
thanks,

any other ideas?

How do you know there is no spark if you didn't pull the plug yet?? And gas from last fall is too old, even if it runs, you have lost a lot of octane and risk detonation problems. Try fresh plug and fresh gas, if you are getting a spark. If no spark, trace your wires and clean and put dielectric grease on all connections. A little corrosion will suddenly make a bike quit. And check kill switch, too.

Good ideas,
thanks

ok,
plug has spark,

don't have a feeler gauge at home to check gap but will do tomm....

plug tip is gray.....no oil residue on it......

drained gas..........

will check petcock screen.....

oil in oil tank and in the lines.......

any ideas so far?

screen in petcock is clean....

engine kicks over......get spark to plug but no firing in the motor....???

I'd check for the actual presence of gasoline in the carburetor bowl.

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

long story short...prob was oil injector quit working....burned hole in piston...

got another engine a NOS 1975 mt125 installed.....what oil mix should I use as I will premix from now on....

started on safe side running 20 to 1 and drove about 3 miles.....cranked and ran great.....then stalled it and would not crank.....waited about 15 min and fired right up..

whats up with that?
bad points,condensor or coil?

plenty of gas, new gas filter.....

if your using synthetic premix, 20-1 seems really, really rich. try 36-1. and yes, i'd at least re gap the points if not at bare minimum, clean em with fine sand paper. make sure carb is clean, if your carb was dirty, it might have been running really lean and burned a hole and not the injector pump. with the pumps, every thing is submerged in oil and wear is minimal, unless you didnt adjust it in relation to cable stretch.

thanks, carb was cleaned also...

I am running my mt250 at 36:1 with castor type oil that claims it can be run at 60:1 I will proably take it out to 40:1 in a little while.